Coronal holes appear dark areas of the corona when viewed in
ultraviolet light. This elongated hole area from January 11, 2002
was one of the largest seen by SOHO. Although they are usually
located at the poles of the Sun, coronal holes can occur other places
as well. The magnetic field lines in a coronal hole extend out into
the solar wind rather than coming back down to the Sun's surface as
they do in other parts of the Sun. Thus, they are often the source
of strong solar wind gusts that carry solar particles into space and
possibly impact the Earth.